Urban sustainability and resilience: What the literature tells us about “lock-ins”?

Inherited system features and challenges that can hinder urban planning initiatives must be taken into consideration before a path towards a sustainable future can be established. By putting the lock-in effect under scrutiny, it is possible to gain valuable insight to emphasize positive lock-ins and to prevent maladaptation and unsustainable solutions. This paper aims to review the current trends of urban studies regarding sustainability, resilience, and the lock-in effect, focusing on both hot topics and mutual integration by following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses for Scoping Reviews (PRISMA-ScR protocol) and analyzing the top-cited articles on these topics from 2015 to 2021 in the Web of Science database. Based on the revised literature, the potential lock-ins of climate-friendly and sustainable urban development are not adequately discussed. Moreover, while urban sustainability and resilience are often treated as overlapping areas, there is a lack of publications that carefully examine their interlinked long-term perspectives for any hindering effects. Supplementary Information The online version contains supplementary material available at 10.1007/s13280-022-01817-w.


SUSTAINABILITY 2015
In the middle of the 2010s, the most cited papers focused on two easily distinguished topicssmart city and compact vs. sprawled areas -and some other horizontal issues. The first group can be formulated by considering the smart city-oriented. They dealt with smart technologies and the smart city itself as a potential solution for modern sustainable cities. The second large group of the selected and most cited literature is about various planning perspectives, indicating the considerable importance of practice-oriented urban studies in the 21 st century. The selected papers of 2015 include only one study that dealt with horizontal climate-related aspects; Chelleri et al. (2015) published one of the very first manuscripts focusing on climate resilience, the lock-in effect, and the related sustainability challenges in urban areas. Their pioneer paper contributes to formulating the scientific discourse about such complex issues, which tries to solve highly interconnected aspects of urban sustainability.

2016
The most cited papers regarding urban sustainability issues indicate that there is a growing body of literature that recognizes the importance of horizontal aspects of highly local-specific sustainability challenges. They argued that small-scale pilot projects are unquestionably needed before increasing the scale of sustainable urban development interventions besides distinguishing those institutional barriers that can hamper the transformation processes; thus, a scale-related horizontal study has been involved in the most cited documents this year well after 2015. The second group of most cited papers from this year encompasses applied studies concerning green buildings and the construction sector; moreover, case studies in the field of assessment of urban sustainability by using macro indicators in the case of Chinese megacities and the analysis of urban carrying capacity. Finally, smart cities and smart interventions were in focus in several collected studies. Summarizing, it can be stated that the most cited urban sustainability papers from 2016 indicated a strong China-orientation, while case studies regarding the numerical analysis of broader urban sustainability or sector-oriented analyses are also among the top articles in this year; however, the resilience-sustainability framework can not be found at all.

2017
In 2017, an interesting trend can be defined among the top-cited articles on the topic since several studies emphasized the contradiction of previously discussed aspects. what can be found in the literature in the previous year. Besides the hereby introduced critical way, two selected articles dealt with the integration of smart and sustainable cities; finally, a considerable group of the studies chosen from this year includes highly practice-oriented papers.

2018
The 2018 trends regarding the mentioned and studied topics within urban sustainability is an exciting mix of the previously introduced aspects from 2015 and 2016. The papers can be grouped into four main bodies. The first one encompasses those studies which dealt with smart city issues and urban sustainability in a general way. The second group of studies includes those articles which focused on green areas from different perspectives; the third large group covers those studies which focused on Chinese urbanization aspects. Finally, Zhang and Li (2018) connected urban resilience and urban sustainability into a common theoretical framework that can tackle long-term path-dependencies, lock-in opportunities, or other non-intended adverse effects of a not carefully developed urban development action.

2019
2019 is the first year when the ten top-cited articles in urban sustainability studies include at least two papers with a solid urban resilience focus. Meerow and Newell (2019) provided a comprehensive urban resilience theory with a hypothetical case of green infrastructure in the U.S. to demonstrate the importance of trade-offs and their spatial and temporal features. Similarly, trade-offs were in the focus of the second resilience-based urban sustainability study written by Bush and Doyon (2019), who dealt with green infrastructure within that topic. Finally, Sharifi (2019) explored the role of urban forms regarding the overall resilience of a given city by arguing the advantages of compact, polycentric, and landscape-connected cities. The rest of the top-cited studies indicate a shift in urban sustainability studies since they all concentrated on the implementation phase; moreover, four articles of the ten analyzed studies were about different aspects of smart cities or utilization of different types of data.

2020
The most cited papers of 2020 represent considerable heterogeneity regarding the discussed topics, while new and highly complex aspects, such as climate change issues, can be found as well. Rice et al. (2020) argued the contradictions of climate-friendly cities and think critically about climate mitigation and adaptation issues within a broader sustainability narrative. Their article joined to that narrative in recent years about potential trade-offs, path-dependencies, and lock-ins of sustainable urban development interventions from a climate-friendly point of view.
As it could be seen in the previous years, social aspects and environmental justice regarding urban green and blue spaces attracted considerable scientific interest. Contrary to the trends observed in last years, only one article dealt with smart city aspects. Finally, several implication-oriented papers have also been involved in the top articles, which assessed the benefits of green infrastructure projects and green.
The 2021 collection of top-cited urban sustainability-oriented papers include those that can attract the most citations in the initial phase of their lives. Therefore, the following short introduction provides only a snapshot instead of a state-of-the-art

RESILIENCE 2015
In 2015 most papers dealt with green infrastructure; half of them quantified their cooling effects or carbon storage and sequestration, while others focused on the policy or conceptual aspects.
Other studies take an emphasis on the concept and implementations of resilience considering the possibilities to broaden resilience from the narrow-minded climate adaptation and catastrophe management perspective to comprehend better global sustainability issues (Chelleri et al., 2015) or elaborate a resilience scoreboard to enhance the integration of local plans (Berke et al., 2015). Baker and Mehmood (2015) investigated social innovations and claimed that they could enhance locally specified sustainability and adaptive transition -it requires a certain level of well-being, needs for social change, and the integrated role of the public/private institutions, civil society, and citizens.

2016
Research on green infrastructure remained in focus in 2016; two out of four were quantitative studies concerning urban heat islands, while the remaining ones focused on the importance of considering non-native species in urban greening and explored the spatial and social differences in residential urban agriculture. Three articles dealt with the resilience concept: a comprehensive literature review (Meerow et al., 2016), which is highly the most cited urban resilience paper in the last six years. The other two approached the concept from the aspect of urban planning. On the one hand, Anguelovski et al. (2016) showed that adaptation strategies could intensify the socio-spatial inequalities, while on the other hand, Mehmood (2016) proposed an evolutionary resilience framework to address long-term challenges and relies on proactive planning and local communities. One of the remaining three studies is about the consequences of private equity real estate investments on rental housing markets. Finally, the last two studies are concerned with urbanization from the approach of and practice regarding the effects of crises on urban development.

2017
The main focus shifted from green infrastructure to the conceptualization of resilience/ SDG 11 and urban planning in 2017 as a consequence of the introduction of the USDG (in 2015) and the New Urban Agenda (in 2016). Three highly cited papers (out of five categorized into 'concept') put the New Urban Agenda into their focus, forms critics concerning inequities, and path-dependence (Kaika, 2017), questions the indicator-based methodology and the urban focus or highlights challenges regarding indicator choosing, data availability, and localization. In addition, Ziervogel et al. (2017) addressed the concept of urban resilience, including both the New Urban Agenda and 100 Resilient City Program, and claim that refocusing resilience is needed in order to deal with siloed approach, inequities, and path-dependence, thus taking emphasis on negotiated resilience, endogenous approximation and entitlement is essential. Three articles focused on green infrastructure; nevertheless, only one paper (Meerow and Newell, 2017) proposed a framework for urban planning which eases the identification of high priority areas for implementing green infrastructure and addresses trade-offs and synergies. Lastly, one article focuses on smart city assessment however takes only marginal emphasis on resilience.

2018
In 2018 similarly to the previous years, green infrastructure, ecosystem services, the concept of resilience and sustainability, and urban planning were in the centrum of the most cited studies. Zhang and Li (2018) reviewed the literature and highlighted differences between urban resilience and urban sustainability regarding research trends, focus, and clusters. They presented a framework in which resilience is considered passive while sustainability is active. They concluded that these paradigms should be regarded jointly to plan rationally. Among green infrastructure studies, two used quantitative methodology to connect urban heat island changes to different types of green infrastructures or landcover changes; three articles focused on ecosystem services. The last three studies consider spatial/urban planning perspectives in connection with rural restructuring in the face of rapid urbanization, the management challenges arising from consideration of forest landscapes as social-ecological systems, and in connection with excessive information, communication, and technological focus of the smart city concept.

2019
In 2019 only one top-cited article analyzed the relationship between characteristics of urban green infrastructure (e.g., size, form, distribution) and UHI magnitude, which compared different green space planning traditions. The main emphasis was predominantly on practice; thus, evaluation of applied adaptation/ sustainable solutions, their (conceptual) consequences on urban resilience, and impedimental factors of implementations are prevailed. Meerow and Newell (2019) concentrated on social and equity aspects of resilience planning presented a framework to identify trade-offs inherited political and scalar difficulties. Similarly, Bush and Doyon (2019) developed a method to help urban planners address (temporal, scale, functional, social equity, and species) trade-offs, but they focused on nature-based solutions. Piggott-McKellar et al. (2019) explored the barriers -rooted in socio-political, resource, and physical systems/processeswhich occurred during the implementation of community-based adaptation projects in the Global South that the barriers are similar to those in the academic literature. These three studies included examining social equity, one of the most significant critics regarding urban resilience; however, they applied a more practice-oriented approach compared to the previous years. Nevertheless, Long & Rice (Long & Rice, 2019) dealt with the theoretical concept of climate urbanism (as the original root of urban resilience) and criticized its political context, insufficient social attention, and infrastructure focus since it diverges from sustainability. Finally, von Wirth et al. (2019) explored the mechanisms of the spread of urban living labs' impacts and their contribution to sustainability; and Sharifi (2019) examined which urban structures contribute to resilience.

2020
The most cited papers of 2020 represent a strong body of green infrastructure research. We found quantitative studies measuring the cooling effects of blue-green infrastructures and tree shading, while other studies analyzed the role of green infrastructure in urban planning. On the other hand, Loughran (2020) highlights from a historical perspective how city planners have used green areas to address not only the economic but socio-cultural difficulties of cities. Ugolini et al. (2020) explored the critical drivers of normal green space usage. They discovered that social isolation during the Covid-19 pandemic resulted in behavior changes in green infrastructure visitation and its motivations. As a consequence of the recent substantial attention on green infrastructure, two review articles appeared among the most cited ones, Yu et al.
(2020) summarized the literature on blue-green spaces' cooling effect, while Chatzimentor et al. (2020) revealed the research patterns in the EU and found a high focus on metropolitan regions, a considerable interest in ecosystem services, and insufficient attention on social factors. One of the last two articles is concerned about the global networks and interconnectedness of the adaptation interventions (Goh, 2020), while the other examines urban morphology and street networks but respects resilience scantly (Boeing, 2020).

2021
In 2021, Covid-19 induced studies were outstanding, and economic resilience also came into the scene. McCartney et al. (2021) examined economic and tourism recovery after the lockdown in Macao and identified the economic environment as a crucial precursor of revival; even though they regarded resilience as equivalent to bouncing back, they noted that the short-term recovery urgency and profit-seeking fail to address previous vulnerabilities. In the face of the epidemic, a radical shift is needed in urban planning both from the aspect of urban agriculture, which has lost its significance regardless of its potential to contribute to resilience and sustainability as a nature-based multifunctional solution (Langemeyer et al., 2021) and from the angle of proximity and accessibility to address the concept of 15-Minute City (Moreno et al., 2021). Following the resilience and urban planning line, Olazabal and Gopegui (2021) evaluated port cities' adaptation strategies for economic and technological credibility and legitimacy. They stated that existing planning requires substantial improvement to be effective, implemented, and achieve long-term sustainability.

LOCK-IN 2015
In the first analyzed year, the selected publications focused mainly on path dependency or lockin areas: housing policy, infrastructure, and regional development case studies. Housing system and policy were in the focus of Stephens et al. (2015) from a considerable infrastructure point of view since a built-up environment can contribute to the existence of path-dependent decisions. Besides, Filion (2015) argued the strong connection between housing policy regarding suburban areas and potential path-dependent future terms. The second group of the top-cited papers moved around several infrastructure-related issues: considering and integrating long-term impacts of infrastructure development initiatives in terms of potential pathdependency were discussed by Malekpour et al. (2015). A regional point-of-view was applied by many who argued the competitiveness of a given cluster or region regarding path-dependent past and future.

2016
The most cited papers regarding path-dependency and lock-in issues from 2016 indicated more heterogeneity of the analyzed topics. Besides housing studies, the second relevant group of selected articles focused on transitions and transformations: Wolfram (2016) defined urban transformative capacity, including ten components, since transformative change require awareness regarding path dependences and cross-scale linkages; Gouldson et al. (2016) analyzed low emission development strategies by focusing on potential lock-ins and coordination between institutions; Affolderbach and Schulz (2016) encouraged to integrate urban geography into transition studies in order to identify and analyze various forms of synergies; finally, Sorensen (2016) studied periurbanization processes through the lens of path dependencies and stated that newly built-up areas need not only infrastructural background but also institutional agents as well which can contribute to the occurrence of long-term lock-ins. The third group was formulated around regional aspects. Finally, the first climate-related study which dealt with potential lock-ins was written by Bouzarovski et al. (2016), who focused on energy poverty issues as a potentially path-dependent sector. According to their assumptions, various socio-technical lock-ins can be defined through the energetically ineffective residential buildings and the outdated energy supply system. The interlinked mitigation issues make this study one of the first top-cited articles focused on thematic locked-in trajectories.

2017
In 2017, the previously introduced topics were in the focus of top-cited articles again (housing policy, regional clusters, and development), with some relevant exceptions. The most climaterelated lock-in analysis was developed by Bouzarovski and Tirado Herrero (2017) regarding energy poverty. According to Kaika (2017), finding path dependencies have a pivotal role instead of focusing on different adjectives regarding the planned cities in the future, such as safe, sustainable, resilient, and inclusive. This latter study dealt with climate-related aspects in a more detailed way.

2018
Housing studies applied path-dependency analysis in the case of a considerable number of topcited papers in 2018 similarly to the previous years by applying relevant social aspects to illustrate long-term negative tendencies in various urban areas; moreover, regional-level assessments were also involved in the most cited studies this year. Besides, local-specific studies in connection with lock-in tendencies can be found amongst the topics of selected studies as well. Sorensen (2018) warned that institutional lock-ins could be identified and revealed when "frozen" institutions hinder the development process regarding continuously changing and transforming urban areas. Similarly, institutional aspects were in focus in Hein (2018)

2019
In 2019, a substantial portion of studies related to path dependency was concerned with the housing market. Regarding regional economic studies, smart specialization was criticized

2020
Studies in 2020 were concentrated around urban governance and urban development patterns. Tightly connected to resilience, 1) an urban planning tool is proposed to reveal different resilience paths based on local aspects to rectify the embedded planning traces (Wardekker et al., 2020), 2) the concept of resilience resistance is introduced referring to the institutional barriers that are created by way of usual operations but hinder the obtainment of resilience through fatigue, complacency and overconfidence (Shamsuddin, 2020), and 3) the impacts of globalism are explored on adaptation actions (namely flood protection) (Goh, 2020). Ohashi and Phelps (2020) tried to detect the path-dependent mechanism in the restructuring of Tokyo's suburban areas, Jiao et al. (2020) analyzed the spatial-temporal patterns of urban land-use efficiency quantitatively and referred to changelessness as path-dependence.

SECTION ITEM PRISMA-ScR CHECKLIST ITEM REPORTED ON PAGE # TITLE
Title 1 Identify the report as a scoping review. 1 ABSTRACT

Structured summary 2
Provide a structured summary that includes (as applicable): background, objectives, eligibility criteria, sources of evidence, charting methods, results, and conclusions that relate to the review questions and objectives.

Rationale 3
Describe the rationale for the review in the context of what is already known. Explain why the review questions/objectives lend themselves to a scoping review approach.

2-3
Objectives 4 Provide an explicit statement of the questions and objectives being addressed with reference to their key elements (e.g., population or participants, concepts, and context) or other relevant key elements used to conceptualize the review questions and/or objectives.

Protocol and registration 5
Indicate whether a review protocol exists; state if and where it can be accessed (e.g., a Web address); and if available, provide registration information, including the registration number.
3 Eligibility criteria 6 Specify characteristics of the sources of evidence used as eligibility criteria (e.g., years considered, language, and publication status), and provide a rationale.

3-4
Information sources 7 Describe all information sources in the search (e.g., databases with dates of coverage and contact with authors to identify additional sources), as well as the date the most recent search was executed.

3-5
Search 8 Present the full electronic search strategy for at least 1 database, including any limits used, such that it could be repeated.

4
Selection of sources of evidence 9 State the process for selecting sources of evidence (i.e., screening and eligibility) included in the scoping review. 4 Data charting process 10 Describe the methods of charting data from the included sources of evidence (e.g., calibrated forms or forms that have been tested by the team before their use, and whether data charting was done independently or in duplicate) and any processes for obtaining and confirming data from investigators.

Data items 11
List and define all variables for which data were sought and any assumptions and simplifications made. 5 Critical appraisal of individual sources of evidence 12 If done, provide a rationale for conducting a critical appraisal of included sources of evidence; describe the methods used and how this information was used in any data synthesis (if appropriate). -

Synthesis of results 13
Describe the methods of handling and summarizing the data that were charted. 5

Selection of sources of evidence 14
Give numbers of sources of evidence screened, assessed for eligibility, and included in the review, with reasons for exclusions at each stage, ideally using a flow diagram.

6
Characteristics of sources of evidence 15 For each source of evidence, present characteristics for which data were charted and provide the citations. 5-13 and S1.
Critical appraisal within sources of evidence 16 If done, present data on critical appraisal of included sources of evidence (see item 12). -

Results of individual sources of evidence 17
For each included source of evidence, present the relevant data that were charted that relate to the review questions and objectives.

Synthesis of results 18
Summarize and/or present the charting results as they relate to the review questions and objectives. 6-13

Summary of evidence 19
Summarize the main results (including an overview of concepts, themes, and types of evidence available), link to the review questions and objectives, and consider the relevance to key groups.

13-14
Limitations 20 Discuss the limitations of the scoping review process. 14

Conclusions 21
Provide a general interpretation of the results with respect to the review questions and objectives, as well as potential implications and/or next steps.

Funding 22
Describe sources of funding for the included sources of evidence, as well as sources of funding for the scoping review. Describe the role of the funders of the scoping review.